The present invention relates to a sheet bundle conveyance apparatus for a bookmaking apparatus in a bookmaking system that aligns sheets printed by an image forming apparatus in a bundle on a tray in the proper page order and binds the sheet bundle to create a booklet. The disclosed bookmaking apparatus may belong to a finishing apparatus of an image forming apparatus such as a printer, printing machine or copier, and an image forming apparatus equipped with the same.
Generally, this kind of apparatus is widely used as a terminal device of an image forming apparatus such as a printer or printing machine, to stack sheets formed with images in page order, then after aligning the sheets into a booklet, a bookmaking system applies adhesive to one edge of the stacked booklet and binds that to a cover sheet.
There are systems that can print a predetermined booklet by printing predetermined information as on-demand printing and automatically binding and covering that booklet, then cut the edges of sheets to finish the booklet.
Japanese Patent Publication No. 2004-209869 discloses a system wherein sheets output from an image forming apparatus are received from a discharge outlet and guided to a discharge path, then stacked and stored in a tray equipped at a lower side of the discharge outlet. The sheet bundle stacked on the tray and the edges of the sheets in the tray are aligned to a correct posture to form a sheet bundle in a horizontal posture. The sheet bundle is turned 90 degrees, and is then guided in a vertical posture to an adhesive application unit for gluing. A cover sheet, supplied from an inserter, is then folded around the glued sheet bundle and after the cover sheet is glued to the sheet bundle, sides of the sheet bundle that are not glued are trimmed to finish the booklet. The finished booklet is then stored in a stacker.
Various methods can be considered to convey a series of sheets stacked in a bundle to a finishing process, such as for the application of adhesive. First, the sheet bundle may be forcefully gripped by a pair of rollers from above and below and the rollers may be rotated to convey the sheet bundle to a predetermined position. This method requires a simple mechanism and a low-cost configuration.
However, there is the problem that the edges of the sheet may become misaligned because the sheet bundle becomes disorganized when nipped by a pair of opposing surface rollers.
Next, gripping means may grip the stacked sheet bundle on the stray from above and below and convey it to the finishing position of the next process. The sheet bundle may be gripped by the gripping means, so the edges of the sheets have comparatively fewer misalignments. However, the conveyance mechanism of the gripping means for gripping a sheet bundle from opposing sides and conveying it to a predetermined position has the problem of being complex.
Normally, gripping means are equipped with pressing members that open and close to nip the sheet bundle and must be of a size large enough to grip the sheet bundle from above and below. Because the nipping force must be high in order to grip the sheet bundle without its pages coming out of alignment, the drive apparatus must be large.
Such a gripping mechanism must also guide the sheet bundle from the stacking tray to a finishing position at the next process by guide means. This guide means has a complex locus of movement to convey a sheet bundle from a tray position at a substantially horizontal posture to an adhesive application position that is substantially vertically postured, as with a bookmaking apparatus.
Though not disclosed by the Japanese reference, this guide means require complex guides to convey a sheet bundle from a horizontal posture to a vertical posture, and the structure of the apparatus frame to support this is complex.
To turn a sheet bundle that is drawn in a substantially horizontal direction to a substantially vertical direction, as in the apparatus disclosed by the Japanese reference, an area for turning over is required between the discharge path and the tray. Accordingly, the overall apparatus becomes larger.
As described above, when conveying a sheet bundle in a vertical posture by gripping means, the gripping force is determined by the size of the clamping members and clamping pressure, and the posture of the sheet bundle may become skewed, or sheets may fall out of the bundle. To prevent this, the surface areas of the clamping members must be enlarged, and the gripping force must be increased, so when handling sheet sizes for the sheet bundle between JISB6 (a small size) and JISA3 (a large size), the clamping surface area has limitations. Also to increase the clamping pressure, the drive sources, such as the motors and actuators must also be larger, and will require greater amounts of electrical power.